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ARCHIVED - Forecasts expire after 24 hours.
Issued
Fri, April 15th, 2022 - 7:00AM
Expires
Sat, April 16th, 2022 - 7:00AM
Forecaster
Andrew Schauer
Avalanche risk The Bottom Line

The avalanche danger is MODERATE above 1000′. Conditions are going to be more reactive today than they have been for the past few days, as a bump in winds will make it possible to trigger wind slab avalanches up to a foot deep. Watch out for heightened avalanche conditions on steep, wind-loaded terrain. The danger is LOW below 1000′.

Special Announcements
  • End of Season Operations:  This will be the final week of daily forecasts. Beginning Monday, April 18, we will only be issuing forecasts on Tuesday, Thursday, Saturday and Sunday. The final forecast will be on Saturday April 30th.
Fri, April 15th, 2022
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
1 - Low
Avalanche risk
0 - No Rating
1 - Low
2 - Moderate
3 - Considerable
4 - High
5 - Extreme
Avalanche risk Avalanche risk Avalanche risk Avalanche risk Avalanche risk
Travel Advice Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential. Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain.
Likelihood of Avalanches Natural and human-triggered avalanches unlikely. Natural avalanches unlikely; human-triggered avalanches possible. Natural avalanches possible; human-triggered avalanches likely. Natural avalanches likely; human-triggered avalanches very likely. Natural and human-triggered avalanches certain.
Avalanche Size and Distribution Small avalanches in isolated areas or extreme terrain. Small avalanches in specific areas; or large avalanches in isolated areas. Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas. Large avalanches in many areas; or very large avalanches in specific areas. Very large avalanches in many areas.
Recent Avalanches
  • Glide Avalanches: There was one very large avalanche on the south side of Eddie’s yesterday, and at least one new release on the front side of Seattle Ridge. At this point it is getting difficult to tell what is new and what is old on Seattle Ridge– there have been at least 7 glide avalanches between the motorized lot and the uptrack this week.
  • There was a large Wet Loose  avalanche on Penguin Ridge near Girdwood yesterday. The avalanche started in the steep rocks and picked up enough snow that it could have buried a person.
Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Likelihood of Avalanches
Terms such as "unlikely", "likely", and "certain" are used to define the scale, with the chance of triggering or observing avalanches increasing as we move up the scale. For our purposes, "Unlikely" means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. "Certain" means that humans will be able to trigger avalanches on many slopes, and natural avalanches are expected.

Size of Avalanches
Avalanche size is defined by the largest potential avalanche, or expected range of sizes related to the problem in question. Assigned size is a qualitative estimate based on the destructive classification system and requires specialists to estimate the harm avalanches may cause to hypothetical objects located in the avalanche track (AAA 2016, CAA 2014). Under this schema, "Small" avalanches are not large enough to bury humans and are relatively harmless unless they carry people over cliffs or through trees or rocks. Moving up the scale, avalanches become "Large" enough to bury, injure, or kill people. "Very Large" avalanches may bury or destroy vehicles or houses, and "Historic" avalanches are massive events capable of altering the landscape.

Signal Word Size (D scale) Simple Descriptor
Small 1 Unlikely to bury a person
Large 2 Can bury a person
Very Large 3 Can destroy a house
Historic 4 & 5 Can destroy part or all of a village
More info at Avalanche.org

After close to a week of sunny skies and stable conditions, easterly winds are expected to increase avalanche danger in the upper elevations today. A low pressure system centered over the Bering Sea is butting up against a high pressure ridge over the eastern Gulf of Alaska and Prince William sound, which should make for a slight increase in winds but no significant precipitation over our area. With sustained speeds of 10-20 mph and gusts of 20-30, we can expect to see some snow blowing around and creating reactive slabs. This will make it possible to trigger avalanches up to a foot deep at and above treeline.

It has been an amazing week for skiing and riding on a stable snowpack, but today’s active weather is going to require a slightly more conservative mindset. Before you get into steep terrain, look carefully for signs of recent or active wind loading. Any snow blowing off ridgelines is a dead giveaway. Other signs may be a bit more subtle, like a smooth, pillowed texture on the surface, or a layer of stiffer snow sitting on top of a layer of soft snow. Our classic red flags are also indicators of unstable snow, including shooting cracks, collapsing, and fresh avalanche activity. Before you get into steep terrain, take some time to hop off your snowmachine or step off the skin track and look for signs of wind loading. Fresh wind slabs will be most likely to be forming just below ridgelines, convex rolls, or in steep gullies. These avalanches may not be enormous, but it will be possible to trigger something big enough to bury a person if the wind forecast verifies.

Cornice Falls: We have seen multiple large cornices fail this week, and they will remain a concern today as the wind picks up. Be sure to keep plenty of space from the edge since they can break farther back then expected. Be sure to limit the time you spend under them, as natural failures will also be possible today.

Wet Loose: It is looking like we are going to see mostly cloudy skies today with some pockets of sun. This will most likely keep the snow surface cooler than the past few days, but if the clouds break up at all we may see some wet loose activity later in the day.

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Avalanche Problem 2
  • Glide Avalanches
    Glide Avalanches
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Glide Avalanches
Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.

Size of Avalanches
Avalanche size is defined by the largest potential avalanche, or expected range of sizes related to the problem in question. Assigned size is a qualitative estimate based on the destructive classification system and requires specialists to estimate the harm avalanches may cause to hypothetical objects located in the avalanche track (AAA 2016, CAA 2014). Under this schema, "Small" avalanches are not large enough to bury humans and are relatively harmless unless they carry people over cliffs or through trees or rocks. Moving up the scale, avalanches become "Large" enough to bury, injure, or kill people. "Very Large" avalanches may bury or destroy vehicles or houses, and "Historic" avalanches are massive events capable of altering the landscape.

Signal Word Size (D scale) Simple Descriptor
Small 1 Unlikely to bury a person
Large 2 Can bury a person
Very Large 3 Can destroy a house
Historic 4 & 5 Can destroy part or all of a village
More info at Avalanche.org

Glide avalanches continue to release in the area, including a very large release yesterday on the south face of Eddie’s. With mostly cloudy skies today, we are less likely to see a lot of releases, but these things are very hard to predict. With all of the recent activity, we know they are on the move. Be sure to limit the time you spend traveling under glide cracks– these avalanches are large and destructive, and it would be very bad to get caught standing under one if the slope released.

This glide avalanche on the south face of Eddie’s yesterday is one of the biggest ones we’ve seen this spring. That crack just to the right of the slope that released is the kind of thing we want to avoid. Photo: M.J. Schauer. 04.14.2022

Weather
Fri, April 15th, 2022

Yesterday: Another day of clear skies, with high temperatures in the low 30’s to mid 40’s F, and overnight lows in the upper teens to upper 20’s F. Winds were light out of the east at 5-10 mph for most of the day, with a slight increase overnight.

Today: Mostly cloudy skies with southeasterly winds at 10-20 mph and gusts of 20-30 mph. We might see some light snow showers but no measurable precipitation. Highs are expected in the upper 20’s to mid 30’s F, with low temperatures in the 20’s F tonight.

Tomorrow: Partly cloudy skies with high temperatures in the upper 20’s to mid 30’s F. Easterly winds are expected to continue at 10-20 mph overnight before dropping down to 5-10 mph during the day tomorrow. Some light snow showers are possible, with no significant accumulation expected.

PRECIPITATION 24-hour data (6am – 6am)

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 34 0 0 109
Summit Lake (1400′) 30 0 0 38
Alyeska Mid (1700′) 38 0 0 N/A

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 26 E 5 22
Seattle Ridge (2400′) 28 SE 8 16
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This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area. This advisory does not apply to highways, railroads or operating ski areas.